Docker CLI

Docker CLI (Command Line Interface) is a powerful tool for interacting with Docker, allowing users to manage containers, images, networks, and volumes through commands in the terminal. Below is a detailed guide covering common Docker commands, flags they accept, and usage examples.

docker pull

Purpose:
This command downloads a Docker image from a registry (such as Docker Hub) to your local machine.

Syntax:

docker pull [OPTIONS] IMAGE[:TAG|@DIGEST]

Flags:

• --all-tags, -a: Download all tags for the image.
• --platform: Specify the platform to pull from (e.g., linux/amd64, linux/arm64).
• --quiet, -q: Suppress output; only shows image ID.

Examples:

1. Pull the latest version of the ubuntu image:

   docker pull ubuntu

2. Pull a specific version of the nginx image:

   docker pull nginx:1.21

3. Pull an image for a specific platform:

   docker pull --platform linux/arm64 ubuntu

4. Pull all tags of an image:

   docker pull --all-tags ubuntu

docker build

Purpose:
This command is used to build a Docker image from a Dockerfile.

Syntax:

docker build [OPTIONS] PATH | URL | -

Flags:

• -f, --file: Specify the Dockerfile to use.
• -t, --tag: Name and optionally tag an image (e.g., image:tag).
• --no-cache: Do not use cache when building the image.
• --build-arg: Set build-time variables.
• --pull: Always attempt to pull a newer version of the image.
• --platform: Set the platform to build for.

Examples:

1. Build an image using the current directory’s Dockerfile:

   docker build -t myapp .

2. Build an image with a specific Dockerfile:

   docker build -f Dockerfile.dev -t myapp .

3. Build an image with no cache:

   docker build --no-cache -t myapp .

4. Build an image for a specific platform:

   docker build --platform linux/amd64 -t myapp .

docker exec

Purpose:
This command allows you to run commands in a running container.

Syntax:

docker exec [OPTIONS] CONTAINER COMMAND [ARG...]

Flags:

• -d, --detach: Run the command in the background.
• -i, --interactive: Keep STDIN open even if not attached.
• -t, --tty: Allocate a pseudo-TTY.

Examples:

1. Execute a command inside a running container (mycontainer) to start a bash shell:

   docker exec -it mycontainer bash

2. Run a command in the background:

   docker exec -d mycontainer touch /tmp/hello.txt

3. Run a command interactively:

   docker exec -it mycontainer ls /app

docker rm

Purpose:
This command removes one or more containers.

Syntax:

docker rm [OPTIONS] CONTAINER [CONTAINER...]

Flags:

• -f, --force: Forcefully remove a running container (use with caution).
• -v, --volumes: Remove the volumes associated with the container.
• --link: Remove the specified link.

Examples:

1. Remove a stopped container (mycontainer):

   docker rm mycontainer

2. Forcefully remove a running container (mycontainer):

   docker rm -f mycontainer

3. Remove a container and its associated volumes:

   docker rm -v mycontainer

docker start

Purpose:
This command starts one or more stopped containers.

Syntax:

docker start [OPTIONS] CONTAINER [CONTAINER...]

Flags:

• -a, --attach: Attach to the container's output.
• -i, --interactive: Keep STDIN open even if not attached.

Examples:

1. Start a stopped container (mycontainer):

   docker start mycontainer

2. Start a container and attach to its output:

   docker start -a mycontainer

docker stop

Purpose:
This command stops one or more running containers.

Syntax:

docker stop [OPTIONS] CONTAINER [CONTAINER...]

Flags:

• -t, --time: Specify a grace period (in seconds) to stop the container. Default is 10 seconds.

Examples:

1. Stop a running container (mycontainer):

   docker stop mycontainer

2. Stop a container with a 5-second grace period:

   docker stop -t 5 mycontainer

docker pause

Purpose:
This command pauses all processes within one or more running containers.

Syntax:

docker pause CONTAINER [CONTAINER...]

Examples:

1. Pause a running container (mycontainer):

   docker pause mycontainer

docker unpause

Purpose:
This command unpauses one or more paused containers, resuming their processes.

Syntax:

docker unpause CONTAINER [CONTAINER...]

Examples:

1. Unpause a paused container (mycontainer):

   docker unpause mycontainer

docker ps

Purpose:
This command lists all running containers.

Syntax:

docker ps [OPTIONS]

Flags:

• -a, --all: Show all containers (default shows only running).
• -q, --quiet: Show only container IDs.
• --filter: Filter containers based on criteria (e.g., status, name).
• --format: Format the output using Go templating.

Examples:

1. List all running containers:

   docker ps

2. List all containers (including stopped ones):

   docker ps -a

3. List only container IDs:

   docker ps -q

4. Filter containers by status:

   docker ps --filter "status=exited"

docker images

Purpose:
This command lists all Docker images on your local machine.

Syntax:

docker images [OPTIONS]

Flags:

• -a, --all: Show all images (including intermediate images).
• -q, --quiet: Show only image IDs.

Examples:

1. List all Docker images:

   docker images

2. List only image IDs:

   docker images -q

docker prune

Purpose:
This command removes unused containers, networks, images, and volumes, helping to clean up disk space.

Syntax:

docker prune [OPTIONS]

Flags:

• --all: Remove all unused images, not just dangling ones.
• --force, -f: Force the prune action without confirmation.
• --volumes: Also prune unused volumes.

Examples:

1. Remove all unused containers, networks, and dangling images:

   docker system prune

2. Remove all unused images (not just dangling):

   docker image prune --all

3. Remove unused volumes:

   docker volume prune

4. Force removal without confirmation:

   docker system prune -f

docker logs

Purpose:
This command fetches logs from a container, useful for debugging and monitoring.

Syntax:

docker logs [OPTIONS] CONTAINER

Flags:

• -f, --follow: Follow the log output (real-time).
• --tail: Show the last N lines of logs.
• --since: Show logs since a specific timestamp.

Examples:

1. View logs of a container (mycontainer):

   docker logs mycontainer

2. Follow logs in real-time:

   docker logs -f mycontainer

3. View the last 100 lines of logs:

   docker logs --tail 100 mycontainer

4. View logs since a specific time:

   docker logs --since "2025-01-12T00:00:00" mycontainer

docker debug

Purpose:
This command is used to provide more detailed information and assist with debugging Docker components.

Syntax:

docker debug

Examples:

• Running docker debug typically gives information about container runtime errors, failed commands, and system diagnostics, though it might require additional debugging tools or flags depending on the environment and context.